Compensating device suitable for use in railway car transformers

ABSTRACT

A compensating device suitable for use in railway car transformers has at least one compensation receptacle in fluid communication connection with the interior of the housing of a transformer and having a fluid volume. A separating element limits the fluid volume in the compensation receptacle. When a change occurs in the fluid volume in the compensation receptacle, the separating element is subject to a change in position. The separating element is designed in the form of a roll-over membrane. The circumferential edge of the membrane is connected to the side walls of the compensation receptacle at a distance form the bottom of the receptacle in a sealing manner. The connection is such that the roll-over membrane, in its rolled-up state, has a position in which it allows for the largest amount of fluid volume by substantially extending in one plane at a distance form the bottom. The membrane can be rolled-out from this position so as to approach the side walls and bottom in the compensation receptacle, reducing the fluid volume.

FIELD OF THE INVENTION

The present invention relates to a compensating device suitable for usein railway car transformers having at least one compensation receptacle.The compensation receptacle has a fluid-carrying connection with theinterior of the housing of the transformer, carries a fluid volume, andhas a separating element limiting the fluid volume in the compensationreceptacle. The separating element is in the form of a membrane having acircumferential border connected with and sealed to the side walls ofthe compensation receptacle at some distance form its bottom. Withmodification of the fluid volume in the compensation receptacles, theseparating element is subject to modification of its position.

BACKGROUND OF THE INVENTION

Work temperatures of from −30 degrees C. to 135 degrees C. prevailduring the operation of transformers in railway cars. The fluid used astransformer fluid, generally in the form of silicon oil, is subject tovolume fluctuations of greater than 10%. In order to be able tocompensate for these temperature-dependent volume fluctuations, acompensation receptacle is conventionally provided which can storetransformer fluid and can deliver the transformer fluid through afluid-carrying connection into the interior of the housing of thetransformer when low operation temperatures prevail. During operation athigh temperatures, it can carry transformer fluid out of the housing ofthe transformer.

In order to be able to fulfill this function, one compensationreceptacle is disclosed in EP 0 743 661 A3. A vertically movable guidedcompensating plate is arranged in the compensation receptacle. The plateserves as a separating element, separating the fluid volume of differentmagnitudes in the compensating receptacle form the ambient atmosphere.To guide the movement of the compensating plate, two sheathings areprovided in the compensation receptacle which slide relative to oneanother. One sheathing is fastened to remain stationary. The othersheathing is fastened to the compensating plate. A spring arrangementlocated within the sheathing produces a prestressing or servo-force,seeking to move the compensating plate in the direction corresponding tothe diminution of volume.

This device of EP 0 743 661 A3 is costly to manufacture, and is ofcomplicated construction which is a considerable disadvantage. Sincetransverse acceleration in the magnitude of 5 g can occur with the useof such compensating devices in transformers for the operation ofrailway cars, the sheathing and spring arrangement, in the compensationreceptacle forming the movable positioning of the compensation plate,must be manufactured very carefully. Construction is costly, if thepredetermined tolerances are to be maintained to avoid disruptions ofoperation when transverse acceleration occurs. On the other hand, thelocation of the sheathing and spring arrangement in the interior of thecompensation receptacle leads to a dead space of considerable volume,because the guiding obtained by the sheathings moving relative to oneanother allows for only a limited length of passage for the movement ofthe compensating plate. As a result, a very unfavorable ratio resultsbetween structural dimensions of the compensation receptacle andmagnitudes of variable fluid volume remaining available as compensationspace.

A compensating device disclosed in U.S. Pat. No. 4,609,900 is suitablefor use with small-format, high voltage transformers, and provides amembrane as separating element. The separating element is guided bymeans of a spring-biased guide member within the compensationreceptacle. In the position corresponding to the smallest volume offluid, the membrane extends into the intermediate space between thecontainer interior wall and the guide member against the bottom of thecompensation receptacle. With wave movements of the guiding memberoccurring counter to the spring force form the bottom, thenon-expandable membrane is laid out in the intermediate space betweenthe receptacle interior wall and guide member in an unrolling foldingover upon itself. Also, with this compensating device of this type, avery unfavorable ratio exists between structural dimensions and thevolume remaining available as compensation space. Additionally, the useof a spring-biased guide member guided on the housing leads to acomplicated and costly construction.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide a compensationreceptacle which can be manufactured of simpler construction and at lowcost, and which is characterized by an improved ratio between structuraldimensions and variable compensation volumes. In a compensating device,these objects according to the present invention are attained in that aroll-over membrane having waves is provided as the membrane. Themembrane can be rolled out with pulling flat of the waves.Correspondingly, in its rolled-up state, the membrane extends in aposition freeing the greatest volume of fluid, essentially in a plane atsome distance form the bottom.

According to the present invention, utilization of a roll-over membraneas separating element on the one hand facilitates particularly simpleconstruction and correspondingly greatly decreased manufacturing costsfor the compensation receptacle. On the other hand, it provides theadvantage that nearly the entire volume of the compensation receptacle,without having a dead space volume present and without dropping inweight, is available as variable compensation volume. This is attainedin that the roll-over membrane is of such dimensions that it extends inrolled-up state practically in a plane in which it frees essentially theentire interior space of the compensation receptacle for the fluidvolume, and that it can be unrolled out of this position into atrough-like or cup-like configuration in which it is closely adjacent tothe interior surface of the compensation receptacle, in other words tothe bottom and the side walls. Thus, an especially good ratio betweenstructural dimensions of the compensation receptacle and dimensions ofusable compensation volume is attained.

A compensation device disclosed in CH-A-436 368 has a membrane as aseparating element, which is not expandable. The membrane is of a metalfoil, on both sides of which is applied a plastic foil. The missingexpandability of the membrane prevents it from extending to the positioncorresponding to the greatest fluid volume in a plane at some distancefrom the bottom. This device is much rather configured as a sphericalvessel in which the membrane is hollowed out convexly or concavely in atrough-like manner.

Another particular advantage of the compensation device according to thepresent invention involves using compensation receptacles, produced in asimple and low-cost method of construction, for the operation of therelevant transformer by a plurality of quite small-volume compensationreceptacles provided in a modular arrangement. When using a plurality ofsmall-volume compensation receptacles constructed together in modularconstruction to form a modular compensation device associated with atransformer, the disturbing influence of the sloshing of the transformerfluid in the compensation receptacle, as it occurs in conventionalcompensation devices, is reduced. With the conventional devices,measures must be taken in order to suppress the destructive influencesof the sloshing occurring with the presence of transverse accelerationcaused by the springing expansion working on the movable compensationplate, which presses the compensation plate on the fluid surface. Withthe present invention, on account of its subdivision of the compensationarrangement into a plurality of small partial volumes, no measures forthe suppression of the sloshing effects are required. Thus, it is notrequired that the roll-over membrane represent a stabilizing element tocounter the sloshing. The surface of the roll-over membrane without anyfurther difficulty can be of such dimensions that even in an entirelyrolled-out state, it corresponds to the smallest fluid volume, havingdimensions which are only slightly smaller than the interior surface ofthe compensation receptacle defining the fluid volume. The roll-overmembrane, even in the state of the smallest fluid volume (in other wordsin completely rolled-out state), stands under only a slight tensilestress.

The modular construction of the compensating device made up of aplurality of compensation receptacles arranged on the transformerhousing permits suitable grouping of the compensation receptacles. Freespaces on the top surface of the transformer housing can then be usedfor cable through-conductance or the like.

Other objects, advantages and salient features of the present inventionwill become apparent from the following detailed description, which,taken in conjunction with the annexed drawings, discloses a preferredembodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings which form a part of this disclosure:

FIG. 1 is a diagrammatically simplified, top plan view of a transformerhousing with compensation receptacles arranged on its top surface in twoside groupings to comprise the compensation device according to thepresent invention, with top sealed coverings of the compensationreceptacles removed;

FIG. 2 is a top plan view, in section and in larger scale, of one of thecompensation receptacles of FIG. 1, likewise without top cover; and

FIG. 3 is a side elevation view in section of the compensationreceptacle taken along line III—III of FIG. 2, but with its top sealedcover replaced.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 the housing 1 of a transformer is filled with transformerfluid 1. On the top of housing 1, eight compensation receptacles inmodular construction are arranged in two side groups of four each toform a compensating device according to the present invention. Betweenthe two groups of compensation receptacles 3, a free space 5 remains onthe top of housing 1. The free space, for example, can be used for cablethrough-conductance or conduit when limited space ratios are provided,in the underfloor construction used with railway cars. Compensationreceptacles 3 are in turn configured as caissons having identicalrectangular foundation plates, and are illustrated in FIGS. 1 and 2without their top sealed covers, which cover 7 is seen only in FIG. 3.

FIGS. 2 and 3 shown the individual unit of a compensation receptacle 3in greater detail. The side walls 11 of the receptacle stand parallel toone another in pairs, extending perpendicularly from bottom or bottomwall 9. For the formation of a fluid-carrying connection with theinterior space of housing 1 of the transformer, flat bottom 9 isprovided with boreholes 13. Cover 7 forming the top sealing of thecaisson-shaped compensation receptacle 3 likewise has boreholes 15 forventilation of the space beneath cover 7.

A frame 17 is screwed into engage with, to extend along the bottom ofcover 7, and to fit to the interior of the top edges of side walls 11.The circumferential border of a roll-over membrane 19 is fastened toframe 17, and is sealed off from the interior surfaces of side walls 11.Frame 17, however, can also be fastened and sealed directly onto cover7.

Roll-over membrane 19, is shown in the drawings in its rolled-up state,in which it extends essentially in a plane along the bottom of top cover7. It can be rolled out by a pressure differential resulting in thepulling out flat of its waves or folds. The membrane assumes atrough-like or cup-like configuration as it approaches bottom 9 and theinterior surfaces of side walls 11 of compensation receptacle 3. Themagnitude of fluid volume 21 found beneath roll-over membrane 19 variesin this case between a value corresponding to almost the entire volumeof caisson-shaped compensation receptacle 3 and a comparably very smallremainder volume. In other words practically the entire interior spaceof compensation receptacle 3 can stand accessible as compensation volumefor inflow or discharge of fluid through boreholes 13. During thecompensation movements of roll-over membrane 19, the space found betweenit and cover 7 is ventilated through boreholes 15 in cover 7. Avalve-operated ventilation mechanism can be series-connected with theboreholes 15 to avoid polluting environmental influences.

The compensating device can be constructed in modular construction insuch a manner that the longitudinal sides of the groups formed ofcompensation receptacles 3 are formed by side walls 11 passing all theway through. In FIG. 2, the right- and left-side walls 11 mounted on theexterior are represented as broken off at 23. The individualcompensation receptacles 3 in turn are compartmentalized by side walls11 running transverse to one another. Likewise the transversearrangement of side walls 11 for the formation of modules could bepassing all the way through two or more compensation receptacles 3.

Roll-over membrane 19 is manufactured of an elastomeric material, forexample a suitable synthetic rubber material, and preferably isreinforced with webbing inserts. A plastic foil coating can be providedon at least one membrane surface by lamination to improve the fluidimpenetrability. Preferably, the surface of roll-over membrane 19 is ofsuch dimensions that even in completely rolled-out state, it remainsunder only a minimal tension, which, despite the moments duringoperation when the temperature is as high as possible, allows for aparticularly long operation life.

Specifically, the membrane in the rolled-out or flattened state has aplanar bottom portion defined between vertical portions of the membraneadjacent side walls 11. The bottom portion has a surface area which isapproximately 4 to 8 percent, and preferably about 6 percent, smallerthan the surface area of bottom 9 between side walls 11.

While a particular embodiment has been chosen to illustrate theinvention, it will be understood by those skilled in the art thatvarious changes and modifications can be made therein without departingfrom the scope of the invention as defined in the appended claims.

What is claimed is:
 1. A compensating device usable with railway cartransformers, comprising: at least one compensation receptacle having aport in fluid communication with an interior of an associatedtransformer housing, and having side walls and a bottom wall; a fluidvolume enclosed within said receptacle; and a separating element withinsaid receptacle limiting said fluid volume in said receptacle, saidseparating element being a roll-over membrane having a circumferentialborder sealingly connected to said side walls at a distance spaced fromsaid bottom wall, said membrane having waves; whereby, upon modificationof said fluid volume, position of said membrane is modified such thatsaid membrane extends substantially in a plane in a rolled-up state withsaid waves at a distance from said bottom wall when said receptaclecontains a maximum fluid volume, and such that said membrane is in arolled-out state with flattening of said waves and with said membranelocated adjacent said bottom wall when said receptacle contains aminimum fluid volume.
 2. A compensating device according to claim 1wherein said receptacle is a caisson with said side walls extending fromsaid bottom wall in pairs parallel to one another in each pair; saidbottom wall comprises a flat, rectangular plate; and saidcircumferential border of said membrane is connected to said side wallsadjacent top borders thereof.
 3. A compensating device according toclaim 2 wherein a cover is mounted at said top borders of said sidewalls; and said membrane has top surface areas, remote from said fluidvolume, engaging said cover in said rolled-up state of said membrane. 4.A compensating device according to claim 3 wherein said part comprisesan opening in said bottom wall; and said cover comprises at least oneopening for ventilating said top surface areas of said membrane.
 5. Acompensating device according to claim 1 wherein said membrane in saidrolled-out state has a substantially planar bottom portion definedbetween vertical portions of said membrane adjacent said side walls,said bottom portion having a surface area which is approximately 4 to 8percent smaller than a surface area of said bottom wall between saidside walls.
 6. A compensating device according to claim 5 wherein saidsurface area of bottom portion is approximately 6 percent smaller thansaid surface area of said bottom wall.
 7. A compensating deviceaccording to claim 1 wherein said membrane is made of elastomericmaterial.
 8. A compensating device according to claim 7 wherein saidelastomeric material is reinforced by a webbing insert.
 9. Acompensating device according to claim 7 wherein said membrane is coatedon at least one surface thereof with a plastic foil.
 10. A compensatingdevice according to claim 9 wherein said plastic foil is laminated onsaid membrane.
 11. A compensating device according to claim 1 wherein aplurality of identically configured compensation receptacles arearranged on a top surface of the transformer housing.
 12. A compensatingdevice according to claim 11 wherein said compensation receptacles aregrouped on the transformer housing to define therebetween a surface areaextending completely across said top surface of the transformer housingfree of other equipment elements and defining a through cable conduit.